3D printing with metals is not new. But the range of metals that can be 3D printed is increasing quickly. We recently told you about a laboratory breakthrough that allows 3D printing of liquid metal structures at room temperature, something that makes many readers think of the film, Terminator 2: Judgment Day. Closer to immediate and useful reality, industrial 3D printer supplier ExOne has added iron infiltrated with bronze, and bonded tungsten, to the range of metal and ceramic powders that can be used with its multi-material M-Flex machines. One of the main reasons the company has seen demand for using iron to 3D print parts instead of its existing stainless steel is its lower cost, Rick Lucas, ExOne’s CTO, told Design News in an interview. Iron costs about 25 percent as much as stainless steel. The cost ratio of materials to total part cost also depends on part size: When making parts smaller than the size of the human hand, materials cost is only about 10 to 15 percent of total part cost.